Of various kinds of fluororesins, a copolymer (PFA) of tetrafluoroethylene (TFE) and perfluoro(alkyl vinyl ether) (PAVE) has excellent characteristics such as heat resistance, chemical resistance, and purity, it is used in melt-molding of pipes for transfer of various kinds of medicinal fluids, joints for pipe laying, transport containers, storage containers, pumps, filter housings, etc., and lining of pipes made of steel, valves, joints, etc., which are used in the manufacturing processes of chemical plants and semiconductors or liquid crystals.
In addition, the PFA has excellent non-tackiness and is used in coating materials of rolls or belts for fixing images of copying machines or in coating of the surfaces of cooking utensils such as frying pans and rice cookers.
Of the aforementioned usages, in pipes (tubes and hoses) for medicinal fluid transfer, a high-temperature process of using medicinal fluids and a high-speed and high-pressure process of the flow velocity of medicinal fluids have recently been in progress. However, in an environment in which thermal expansion and contraction are repeated, the durability against deformation stresses is insufficient in the conventional well-known PFA, so PFA with higher durability has been in demand. In addition, even in fixers of copying machines, etc., the durability improvement of the PFA has been in demand along with a high-temperature process and a high-speed process of fixing rolls and belts and thinning of PFA coatings.
Several attempts to improve the durability of the PFA have been made up to now (U.S. Pat. No. 5,932,673, Japanese Kokai Patent Application Nos. 2002-3514 and 2004-161921, etc.), which will be mentioned later. However, PFA capable of responding to the demand of the aforementioned durability improvement is not yet proposed in these attempts.